1. Field of the Invention
This invention generally relates to an AC current detection circuit used in an X-ray apparatus and, more particularly, to an AC current detection circuit for a rotor driving supply source of a rotating anode X-ray tube.
2. Description of the Prior Art
In a conventional detection circuit of this kind mentioned in this preamble, a detecting resistor having a considerably low resistance is interposed between an AC rotor driving supply source and a stator coil of a rotating anode X-ray tube. The resultant AC detection voltage built-up across the detection resistor is rectified through a Zener diode bridge to obtain the lower DC detection voltage at the output of the bridge. Accordingly, the AC current in the rotor driving supply source can be detected by controlling a relay connected to the output of the bridge. However, in a circuit such as an AC rotor driving supply source for a rotating anode X-ray tube, the load has inductive characteristics and a voltage to be applied to the load must be varied (e.g., during the starting period of the rotor, a starting voltage which is about twice the drive voltage is applied to the stator coil). Elements of large power dissipation is then required for measurements of the AC current detection circuit, and also a great power loss is caused by the detecting resistor.